This invention relates generally to gas turbine engines, and more specifically to a method and apparatus for detecting airflow reversal in a sump system.
At least some known gas turbine engines include at least one bearing assembly that rotatably supports a shaft. The bearing assembly is lubricated with oil, which also absorbs and dissipates heat from the bearing and other engine components. Bearing assemblies are housed within sumps that include a supply pump that supplies lubricating oil under pressure to the bearing assemblies, and a scavenge pump that removes spent oil from the sump. Seal assemblies facilitate minimizing oil leakage from the sump along the rotor shaft.
To further facilitate reducing oil leakage from the sump, at least some known bearing assembly sumps are located within pressurized cavities that include seals that extend around the rotor shaft. During operation, compressed air is supplied to pressurize the sump cavity. The sump is also vented to allow continuous air flow through the sump and to prevent oil leakage from sump seals. In at least some known engines, vent pressure is monitored at a vent exit downstream from the sump. However, if the vent air flow becomes inhibited, pressure increases in the sump may go undetected until an over-pressurization condition occurs that is sufficient to cause flow reversal across a sump seal. With either of these conditions, oil can leak out and accumulate in the rotor system causing sub-synchronous vibrations which can result in severe engine damage.
In one aspect, a method is provided for detecting airflow reversal in a sump system of a gas turbine engine. The method includes positioning a first pressure sensor at a sump vent to sense a discharge flow pressure from a sump within the sump system, positioning a second pressure sensor in the sump to sense a pressure in the sump, comparing the sensed pressures obtained from the first and second pressure sensors to determine a pressure difference, and comparing the pressure difference to a predetermined maximum allowable pressure difference.
In another aspect, an apparatus for detecting sump airflow reversal in a vented sump in a gas turbine engine is provided. The apparatus includes a first pressure sensor coupled in flow communication with a sump vent for sensing a sump pressure at the sump vent. The first pressure sensor is configured to produce a first signal indicative of the sensed pressure. A second pressure sensor is positioned within the sump for sensing a sump pressure therein. The second pressure sensor is configured to produce a second signal indicative of the sensed pressure. An output device is coupled to the first and second pressure sensors and is configured to receive and display pressure indications based on the first and second signals.
In another aspect, a gas turbine engine is provided that includes a compressor, a turbine, a shaft assembly coupling the compressor and the turbine, and a support assembly rotatably supporting said shaft assembly. A sump system for collecting oil from the support assembly includes a detection system for detecting operating pressures in the sump system. An engine monitoring system is coupled to the detection system for detecting air flow reversal in the sump system.